1. Field of the Invention
The present invention relates generally to optics and, more specifically, the present invention relates to optical waveguide tapers.
2. Background Information
Internet and network data traffic growth rate is pushing a desire for optical-based data communication. Transmission of multiple optical channels over the same fiber in dense wavelength-division multiplexing (DWDM) systems and Gigabit Ethernet (GBE) systems provide a simple way to use the higher data capacity (signal bandwidth) offered by fiber optics. Commonly used optical components in data communications systems include wavelength division multiplexed (WDM) transmitters and receivers, optical filters such as diffraction gratings, thin-film filters, fiber Bragg gratings, arrayed-waveguide gratings, optical add/drop multiplexers, modulators, lasers and optical switches.
Many of these building block optical components can be implemented in semiconductor devices. As such, the semiconductor devices are typically connected to optical fibers. Three-dimensional tapered waveguides or mode size converters are typically used to couple light between a semiconductor waveguide device and a fiber because semiconductor waveguide devices usually have smaller mode sizes compared to optical fiber mode sizes. The semiconductor waveguides allow the light to propagate through a photonic chip that contains various components such as a modulator, switch, multiplexer, and so on. The large differences in refractive index possible in semiconductor waveguide systems allow for the smaller waveguide dimensions.
Silicon photonic integrated chips (PIC) are used for high-speed optical interconnects, for modulation and for switching. As the size of a silicon waveguide in a PIC is usually much smaller than the core diameter of an optic fiber, a waveguide taper is used. The taper directs and expands the optical modal size of the silicon waveguide to match the optic fiber.